My partner has Seasonal Affective Disorder and the dark days of winter really affect her. To cheer her up I decided to try an show her how, coming out of winter, that the length of the day will increase fairly rapidly through spring settling into the long days of summer.
I decided that I could do this with a bit of geometry and some code.
Our planet earth is spheroidal, and so circles suffice to summarise it in two dimensions on paper. It is the axial tilt of 23.5 degrees that is primarily responsible for seasonality. That seasonality becomes greater within a year as latitude (or the distance from the equator) increases.
Drawing a circle and the tilted axis of rotation, the points of intersection become the true poles at 9O degrees N and S, respectively. The equator in our schematic is a line that runs perpendicular (at 90 degrees) to axis of rotation, and that is 0 degrees. We also draw a vertical line through the circle. This symbolises the two sides of earth; one half receiving light from the sun, and one half in darkness. From there we can pick a latitude. In the example, it is 60 degrees north.